EMC of wireless medical telemeters and noise radiated from light emitting diode lamps

Light Emitting Diode (LED) lamps have become widespread, not only in homes but in clinical settings. However, electromagnetic noise from LED lamps could be problematic. In the healthcare field, the reception level of signals from medical telemeters might decrease after replacing traditional lighting with LED lamps. To investigate the effects of noise radiated from LED lamps on medical telemeters, we measured the electric field intensity of 34 types of LED lamps, many of which emit noise in the 400 MHz band. Some types of LED lamps had increased floor level noise of 30 dB. Artifact noise was observed on electrocardiogram and respiratory waveforms when an LED lamp was placed next to the monitor. This effect was observed if the separation distance between a medical telemetry transmitter and a monitor was quite close. When approximately 5 m apart, signals to the monitors were received normally. In hospitals, AC power supply cables are often placed near transmission cables, as are leaky coaxial cables (LCX) attached to the monitors. To prevent interference with medical telemeters, selecting low noise LED lamps and maintaining sufficient separation between LED lamps and receiving antennas and coaxial cables is necessary.